revenue from contracts with customers (Tables)


	June 30,		December 31,
As at (millions)	2019		2018
Estimated minimum transaction price allocated to remaining unfulfilled, or partially unfulfilled, performance obligations to be recognized as revenue in a future period 1, 2
During the 12-month period ending one year hence	$	2,390	$	2,306
During the 12-month period ending two years hence		888		933
Thereafter		29		24
	$	3,307	$	3,263

(1)

Excludes constrained variable consideration amounts, amounts arising from contracts originally expected to have a duration of one year or less and, as a permitted practical expedient, amounts arising from contracts that are not affected by revenue recognition timing differences arising from transaction price allocation or from contracts under which we may recognize and bill revenue in an amount that corresponds directly with our completed performance obligations.

(2)

IFRS-IASB requires the explanation of when we expect to recognize as revenue the amounts disclosed as the estimated minimum transaction price allocated to remaining unfulfilled, or partially unfulfilled, performance obligations. The estimated amounts disclosed are based upon contractual terms and maturities. Actual minimum transaction price revenues recognized, and the timing thereof, will differ from these estimates primarily due to the frequency with which the actual durations of contracts with customers do not match their contractual maturities.


		June 30,		December 31,
As at (millions)	Note	2019		2018
Customer accounts receivable		$	1,285	$	1,263
Accrued receivables – customer			179		175
Allowance for doubtful accounts	4		(42)		(53)
			1,422		1,385
Accrued receivables – other			413		215
		$	1,835	$	1,600


		Three months				Six months
Periods ended June 30 (millions)	Note	2019		2018		2019		2018
Balance, beginning of period		$	1,449	$	1,279	$	1,475	$	1,303
Net additions arising from operations			350		303		671		584
Amounts billed in period and thus reclassified to accounts receivable 1			(357)		(313)		(703)		(617)
Change in impairment allowance, net	4		(2)		2		(4)		1
Other			1		1		2		1
Balance, end of period		$	1,441	$	1,272	$	1,441	$	1,272
To be billed and thus reclassified to accounts receivable during:
The 12-month period ending one year hence						$	1,019	$	907
The 12-month period ending two years hence							407		354
Thereafter							15		11
Balance, end of period						$	1,441	$	1,272
Reconciliation of contract assets presented in the Consolidated statements of financial position – current
Gross contract assets						$	1,019	$	907
Reclassification to contract liabilities of contracts with contract assets less than contract liabilities	24						(5)		(5)
Reclassification from contract liabilities of contracts with contract liabilities less than contract assets	24						(155)		(142)
						$	859	$	760

(1)

For the three-month and six-month periods ended June 30, 2019, amounts billed for our wireless segment and reclassified to accounts receivable totalled $330 (2018 – $287) and $650 (2018 – $567),respectively.